Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -43,6 +43,7 @@
 option(LIBCXX_ENABLE_CXX1Y "Enable -std=c++1y and use of c++1y language features if the compiler supports it." OFF)
 option(LIBCXX_ENABLE_SHARED "Build libc++ as a shared library." ON)
 option(LIBCXX_INSTALL_SUPPORT_HEADERS "Install libc++ support headers." ON)
+option(LIBCXX_GENERATE_COVERAGE "Generate code coverage results from the tests." OFF)
 if (LIBCXX_BUILT_STANDALONE)
   set(LLVM_USE_SANITIZER "" CACHE STRING
       "Define the sanitizer used to build the library and tests")
@@ -231,6 +232,11 @@
 string(REPLACE ";" " " LIBCXX_CXX_FEATURE_FLAGS "${LIBCXX_CXX_FEATURE_FLAGS}")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${LIBCXX_CXX_FEATURE_FLAGS}")
 
+if (LIBCXX_GENERATE_COVERAGE)
+  include(LibcxxCodeCoverage)
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${LIBCXX_CXX_COVERAGE_FLAGS}")
+endif()
+
 #===============================================================================
 # Setup Source Code
 #===============================================================================
Index: cmake/Modules/LibcxxCodeCoverage.cmake
===================================================================
--- /dev/null
+++ cmake/Modules/LibcxxCodeCoverage.cmake
@@ -0,0 +1,41 @@
+
+find_program(LIBCXX_GCOV gcov)
+if (NOT LIBCXX_GCOV)
+  message(FATAL_ERROR "Cannot find gcov...")
+endif()
+
+find_program(LIBCXX_LCOV lcov)
+find_program(LIBCXX_GENHTML genhtml)
+
+set(LIBCXX_CXX_COVERAGE_FLAGS "-g -O0 --coverage -fprofile-arcs -ftest-coverage")
+
+function(setup_lcov_test_target_coverage _coverage_dir)
+  if (NOT LIBCXX_LCOV)
+    message(FATAL_ERROR "Cannot find lcov...")
+  endif()
+  if (NOT LIBCXX_GENHTML)
+    message(FATAL_ERROR "Cannot find genhtml...")
+  endif()
+
+  file(MAKE_DIRECTORY ${_coverage_dir})
+
+  add_custom_command(TARGET cxx
+        PRE_BUILD
+        COMMAND ${LIBCXX_LCOV} --directory . --directory ${_SRC_BUILD_DIR} --zerocounters
+        WORKING_DIRECTORY ${_coverage_dir}
+        COMMENT "Reseting code coverage information.")
+
+  set(_SRC_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR}/../lib/CMakeFiles/cxx.dir/__/src/)
+  set(_CHMOD_END "{} \\$<SEMICOLON>")
+  separate_arguments(_CHMOD_END)
+  add_custom_target(check-libcxx-coverage
+        COMMAND ${LIBCXX_LCOV} --directory . --directory ${_SRC_BUILD_DIR} --capture --output-file libcxx_coverage.info
+        COMMAND ${LIBCXX_LCOV} --remove libcxx_coverage.info 'test/*' 'test/*/*' '/usr/*' '/usr/include/*' --output-file libcxx_coverage.info
+        COMMAND ${LIBCXX_GENHTML} --demangle-cpp -o libcxx_coverage libcxx_coverage.info
+        COMMAND ${CMAKE_COMMAND} -E remove libcxx_coverage.info
+        COMMAND ${CMAKE_COMMAND} -E remove_directory ${_coverage_dir}/test
+        COMMAND find libcxx_coverage/ -type d -exec chmod 750 ${_CHMOD_END}
+        COMMAND find libcxx_coverage/ -type f -exec chmod 640 ${_CHMOD_END}
+        WORKING_DIRECTORY ${_coverage_dir}
+        COMMENT "Generating coverage results")
+endfunction()
Index: lib/CMakeLists.txt
===================================================================
--- lib/CMakeLists.txt
+++ lib/CMakeLists.txt
@@ -43,7 +43,7 @@
 append_if(libraries LIBCXX_HAS_RT_LIB rt)
 append_if(libraries LIBCXX_HAS_GCC_S_LIB gcc_s)
 
-#if LIBCXX_CXX_ABI_LIBRARY_PATH is defined we want to add it to the search path.
+# if LIBCXX_CXX_ABI_LIBRARY_PATH is defined we want to add it to the search path.
 if (DEFINED LIBCXX_CXX_ABI_LIBRARY_PATH)
   target_link_libraries(cxx "-L${LIBCXX_CXX_ABI_LIBRARY_PATH}")
 endif()
@@ -51,7 +51,11 @@
 
 # Setup flags.
 append_if(compile_flags LIBCXX_HAS_FPIC_FLAG -fPIC)
-append_if(link_flags LIBCXX_HAS_NODEFAULTLIBS_FLAG -nodefaultlibs)
+# FIXME: Currently -nodefaultlibs causes the tests not to link when using
+# code coverage due to the order of the libraries passed to the linker.
+if (NOT LIBCXX_GENERATE_COVERAGE)
+  append_if(link_flags LIBCXX_HAS_NODEFAULTLIBS_FLAG -nodefaultlibs)
+endif()
 
 if ( APPLE )
   if ( CMAKE_OSX_DEPLOYMENT_TARGET STREQUAL "10.6" )
Index: test/CMakeLists.txt
===================================================================
--- test/CMakeLists.txt
+++ test/CMakeLists.txt
@@ -28,6 +28,10 @@
   set(LIBCXX_BINARY_DIR ${CMAKE_BINARY_DIR})
   set(PYTHON_EXECUTABLE ${PYTHON_EXECUTABLE})
   pythonize_bool(LIBCXX_ENABLE_SHARED)
+  pythonize_bool(LIBCXX_GENERATE_COVERAGE)
+  if (LIBCXX_GENERATE_COVERAGE)
+    set(LIBCXX_COVERAGE_DIR "${CMAKE_CURRENT_BINARY_DIR}/coverage")
+  endif()
 
   set(AUTO_GEN_COMMENT "## Autogenerated by libcxx configuration.\n# Do not edit!")
 
@@ -43,6 +47,11 @@
             ${CMAKE_CURRENT_BINARY_DIR}
     DEPENDS cxx
     COMMENT "Running libcxx tests")
+
+  if (LIBCXX_GENERATE_COVERAGE)
+    include(LibcxxCodeCoverage)
+    setup_lcov_test_target_coverage(${LIBCXX_COVERAGE_DIR})
+  endif()
 else()
   message(WARNING "Could not find Python, no check target will be available!")
 endif()
Index: test/lit.cfg
===================================================================
--- test/lit.cfg
+++ test/lit.cfg
@@ -28,31 +28,53 @@
       FOO.fail.cpp - Negative test case which is expected to fail compilation.
     """
 
-    def __init__(self, cxx_under_test, use_verify_for_fail,
-                 cpp_flags, ld_flags, exec_env):
+    def __init__(self, cxx_under_test, cpp_flags, ld_flags, exec_env,
+                 test_root,
+                 use_verify_for_fail = False,
+                 generate_coverage = False,
+                 coverage_flags=[],
+                 coverage_root = None,
+                 use_scan_build = None,
+                 scan_build_output = None,
+                 scan_build_args = [],
+                 use_clang_tidy = None,
+                 clang_tidy_args = []):
         self.cxx_under_test = cxx_under_test
         self.use_verify_for_fail = use_verify_for_fail
         self.cpp_flags = list(cpp_flags)
         self.ld_flags = list(ld_flags)
         self.exec_env = dict(exec_env)
-
-    def execute_command(self, command, in_dir=None):
-        kwargs = {
-            'stdin' :subprocess.PIPE,
-            'stdout':subprocess.PIPE,
-            'stderr':subprocess.PIPE,
-        }
-        if in_dir:
-            kwargs['cwd'] = in_dir
-        p = subprocess.Popen(command, **kwargs)
-        out,err = p.communicate()
-        exitCode = p.wait()
-
-        # Detect Ctrl-C in subprocess.
-        if exitCode == -signal.SIGINT:
-            raise KeyboardInterrupt
-
-        return out, err, exitCode
+        self.test_root = str(test_root)
+        self.generate_coverage = generate_coverage
+        self.coverage_flags = list(coverage_flags)
+        self.coverage_root = str(coverage_root)
+        self.use_scan_build = use_scan_build
+        self.scan_build_output = scan_build_output
+        self.scan_build_args = list(scan_build_args)
+        self.use_clang_tidy = use_clang_tidy
+        self.clang_tidy_args = list(clang_tidy_args)
+
+    def execute_command_and_report(self, command, cwd=None, env=None, compile_cmd=None):
+        exec_env = dict(os.environ)
+        if env:
+            exec_env.extend(env)
+        out,err,exitCode = lit.util.executeCommand(command, cwd=cwd, env=exec_env)
+        report = ''
+        if compile_cmd:
+            report += """Compiled with: %s\n""" % \
+                ' '.join(["'%s'" % a for a in compile_cmd])
+        report += """Command: %s\n""" % \
+                ' '.join(["'%s'" % a for a in command])
+        if env:
+            report += """Environment: %s\n""" % \
+                ' '.join(["'%s'='%s'" % (k,env[k]) for k in env])
+        report += """Exit Code: %d\n""" % exitCode
+        if out:
+            report += """Standard Output:\n--\n%s--""" % out
+        if err:
+            report += """Standard Error:\n--\n%s--""" % err
+        report += '\n\n'
+        return report, exitCode, out, err
 
     def execute(self, test, lit_config):
         while True:
@@ -63,22 +85,33 @@
                     raise
                 time.sleep(0.1)
 
+    def _handle_metadata_line(self, ln, tag, out):
+        if tag not in ln:
+            return False
+        items = ln[ln.index(tag) + len(tag):].split(',')
+        items = [s.strip() for s in items if s.strip()]
+        out.extend(items)
+        return True
+
     def _execute(self, test, lit_config):
         # Extract test metadata from the test file.
         requires = []
         unsupported = []
+        unsupported_xfail = []
+        requires_xfail = []
         use_verify = False
         with open(test.getSourcePath()) as f:
             for ln in f:
-                if 'XFAIL:' in ln:
-                    items = ln[ln.index('XFAIL:') + 6:].split(',')
-                    test.xfails.extend([s.strip() for s in items])
-                elif 'REQUIRES:' in ln:
-                    items = ln[ln.index('REQUIRES:') + 9:].split(',')
-                    requires.extend([s.strip() for s in items])
-                elif 'UNSUPPORTED:' in ln:
-                    items = ln[ln.index('UNSUPPORTED:') + 12:].split(',')
-                    unsupported.extend([s.strip() for s in items])
+                if self._handle_metadata_line(ln, 'REQUIRES-XFAIL:', requires_xfail):
+                    pass
+                elif self._handle_metadata_line(ln, 'UNSUPPORTED-XFAIL:', unsupported_xfail):
+                    pass
+                elif self._handle_metadata_line(ln, 'XFAIL:', test.xfails):
+                    pass
+                elif self._handle_metadata_line(ln, 'REQUIRES:', requires):
+                    pass
+                elif self._handle_metadata_line(ln, 'UNSUPPORTED:', unsupported):
+                    pass
                 elif 'USE_VERIFY' in ln and self.use_verify_for_fail:
                     use_verify = True
                 elif not ln.strip().startswith("//") and ln.strip():
@@ -92,100 +125,144 @@
         # introducing a dependency there. What we more ideally would like to do
         # is lift the "requires" handling to be a core lit framework feature.
         missing_required_features = [f for f in requires
-                                     if f not in test.config.available_features]
+                                     if f not in test.config.available_features
+                                     or f not in test.config.target_triple]
         if missing_required_features:
             return (lit.Test.UNSUPPORTED,
                     "Test requires the following features: %s" % (
                       ', '.join(missing_required_features),))
 
         unsupported_features = [f for f in unsupported
-                             if f in test.config.available_features]
+                             if f in test.config.available_features
+                             or f in test.config.target_triple]
         if unsupported_features:
             return (lit.Test.UNSUPPORTED,
                     "Test is unsupported with the following features: %s" % (
                        ', '.join(unsupported_features),))
 
-        # Evaluate the test.
-        return self._evaluate_test(test, use_verify, lit_config)
+        # Compute list of features that make a test unsupported but also check
+        # that it fails
+        missing_required_xfail_features = [f for f in requires_xfail
+                                    if f not in test.config.available_features
+                                   and f not in test.config.target_triple]
+        unsupported_xfail_features = [f for f in unsupported_xfail
+                             if f in test.config.available_features
+                             or f in test.config.target_triple]
 
-    def _evaluate_test(self, test, use_verify, lit_config):
+        # Dispatch the test based on name and execute it.
         name = test.path_in_suite[-1]
-        source_path = test.getSourcePath()
-        source_dir = os.path.dirname(source_path)
+        if name.endswith('.pass.cpp'):
+            status,report,msg = self._evaluate_pass_test(test, lit_config)
+        elif name.endswith('.fail.cpp'):
+            status,report,msg = self._evaluate_fail_test(test, lit_config, use_verify)
+        else:
+            lit_config.fatal('Unrecognized test suffix: %s' % name)
+
+        # If the test is REQUIRES-XFAIL on UNSUPPORTED-XFAIL translate the
+        # result of the test to reflect that.
+        if len(missing_required_xfail_features) != 0 or \
+           len(unsupported_xfail_features) != 0:
+            if status == lit.Test.FAIL:
+                return lit.Test.PASS,""
+            elif status == lit.Test.PASS:
+                report += "Test unexpectedly passed!"
+                return lit.Test.XPASS, report
+            else:
+                # TODO figure out what generates this
+                assert False
+        # Otherwise check for an error message and return the result
+        if msg:
+            report += msg
+        return status,report
 
-        # Check what kind of test this is.
-        assert name.endswith('.pass.cpp') or name.endswith('.fail.cpp')
-        expected_compile_fail = name.endswith('.fail.cpp')
 
-        # If this is a compile (failure) test, build it and check for failure.
-        if expected_compile_fail:
-            cmd = [self.cxx_under_test, '-c',
+    def _evaluate_fail_test(self, test, lit_config, use_verify):
+        source_path = test.getSourcePath()
+        cmd = [self.cxx_under_test, '-c',
                    '-o', '/dev/null', source_path] + self.cpp_flags
-            expected_rc = 1
-            if use_verify:
-                cmd += ['-Xclang', '-verify']
-                expected_rc = 0
-            out, err, rc = self.execute_command(cmd)
-            if rc == expected_rc:
-                return lit.Test.PASS, ""
-            else:
-                report = """Command: %s\n""" % ' '.join(["'%s'" % a
-                                                         for a in cmd])
-                report += """Exit Code: %d\n""" % rc
-                if out:
-                    report += """Standard Output:\n--\n%s--""" % out
-                if err:
-                    report += """Standard Error:\n--\n%s--""" % err
-                report += "\n\nExpected compilation to fail!"
-                return lit.Test.FAIL, report
+        expectedExitCode = 1
+        if use_verify:
+            cmd += ['-Xclang', '-verify']
+            expectedExitCode = 0
+        report,exitCode,_,_ = self.execute_command_and_report(cmd)
+        if exitCode == expectedExitCode:
+            return lit.Test.PASS, report, ""
         else:
-            exec_file = tempfile.NamedTemporaryFile(suffix="exe", delete=False)
-            exec_path = exec_file.name
-            exec_file.close()
+            return lit.Test.FAIL, report, "Expected compilation to fail!"
 
+
+    def _evaluate_pass_test(self, test, lit_config):
+        source_path = test.getSourcePath()
+        source_dir = os.path.dirname(source_path)
+        report = ""
+
+        # If we are generating code coverage data run the compile command from
+        # the directory the .gcno and .gcda files should be put in.
+        build_cwd = None
+        if self.generate_coverage:
+            source_dir_str = str(os.path.realpath(source_dir))
+            # Subtract the test prefix "/.../libcxx/test/" from the test file directory.
+            build_cwd = source_dir_str[len(str(self.test_root)) + 1:]
+            # Set build_cwd to "/.../build-libcxx/test/coverage/test/.../path-to-test-dir"
+            build_cwd = str(os.path.join(self.coverage_root, 'test', build_cwd))
+            # Recursivly create the directory
             try:
-                compile_cmd = [self.cxx_under_test, '-o', exec_path,
-                       source_path] + self.cpp_flags + self.ld_flags
-                cmd = compile_cmd
-                out, err, exitCode = self.execute_command(cmd)
-                if exitCode != 0:
-                    report = """Command: %s\n""" % ' '.join(["'%s'" % a
-                                                             for a in cmd])
-                    report += """Exit Code: %d\n""" % exitCode
-                    if out:
-                        report += """Standard Output:\n--\n%s--""" % out
-                    if err:
-                        report += """Standard Error:\n--\n%s--""" % err
-                    report += "\n\nCompilation failed unexpectedly!"
-                    return lit.Test.FAIL, report
+                os.makedirs(build_cwd)
+            except:
+                pass
 
+        exec_file = tempfile.NamedTemporaryFile(suffix="exe", delete=False)
+        exec_path = exec_file.name
+        exec_file.close()
+
+        try:
+            if self.use_clang_tidy:
+                status,report,msg = self._execute_clang_tidy_test(source_path)
+                if status != lit.Test.PASS:
+                    return status,report,msg
+
+            compile_cmd = [self.cxx_under_test, '-o', exec_path,
+                        source_path] + self.cpp_flags + self.ld_flags
+            if self.generate_coverage:
+                compile_cmd += self.coverage_flags
+            if self.use_scan_build:
+                cmd = [self.use_scan_build, '--status-bugs',
+                        '-o', self.scan_build_output] + self.scan_build_args
+            else:
                 cmd = []
-                if self.exec_env:
-                    cmd.append('env')
-                    cmd.extend('%s=%s' % (name, value)
-                               for name,value in self.exec_env.items())
-                cmd.append(exec_path)
-                if lit_config.useValgrind:
-                    cmd = lit_config.valgrindArgs + cmd
-                out, err, exitCode = self.execute_command(cmd, source_dir)
-                if exitCode != 0:
-                    report = """Compiled With: %s\n""" % \
-                        ' '.join(["'%s'" % a for a in compile_cmd])
-                    report += """Command: %s\n""" % \
-                        ' '.join(["'%s'" % a for a in cmd])
-                    report += """Exit Code: %d\n""" % exitCode
-                    if out:
-                        report += """Standard Output:\n--\n%s--""" % out
-                    if err:
-                        report += """Standard Error:\n--\n%s--""" % err
-                    report += "\n\nCompiled test failed unexpectedly!"
-                    return lit.Test.FAIL, report
-            finally:
-                try:
-                    os.remove(exec_path)
-                except:
-                    pass
-        return lit.Test.PASS, ""
+            cmd += compile_cmd
+            report,exitCode,_,_ = self.execute_command_and_report(cmd, cwd=build_cwd)
+            if exitCode != 0 or (self.use_scan_build and
+                                (not os.path.exists(exec_path)
+                                 or os.path.getsize(exec_path) == 0)):
+                return lit.Test.FAIL, report, "Compilation failed unexpectedly!"
+
+            cmd = []
+            cmd.append(exec_path)
+            if lit_config.useValgrind:
+                cmd = lit_config.valgrindArgs + cmd
+            report,exitCode,_,_ = self.execute_command_and_report(cmd,
+                                    cwd=source_dir,
+                                    env=self.exec_env,
+                                    compile_cmd=compile_cmd)
+            if exitCode != 0:
+                return lit.Test.FAIL, report, "Compiled test failed unexpectedly!"
+
+        finally:
+            try:
+                os.remove(exec_path)
+            except:
+                pass
+        return lit.Test.PASS, report, ""
+
+
+    def _execute_clang_tidy_test(self, source_file):
+        cmd = [self.use_clang_tidy] + self.clang_tidy_args + [source_file]
+        cmd += ['--'] + self.cpp_flags
+        report,exitCode,out,_ = self.execute_command_and_report(cmd)
+        if exitCode != 0 or len(out) != 0:
+            return lit.Test.FAIL, report, "Compilation failed unexpectedly!"
+        return lit.Test.PASS, report, ""
 
 
 class Configuration(object):
@@ -195,12 +272,21 @@
         self.cxx = None
         self.src_root = None
         self.obj_root = None
+        self.test_root = None
         self.env = {}
         self.compile_flags = []
         self.library_paths = []
         self.link_flags = []
+        self.generate_coverage = False
+        self.coverage_flags = []
+        self.coverage_root = None
         self.use_system_lib = False
         self.use_clang_verify = False
+        self.use_scan_build = None
+        self.scan_build_output = None
+        self.scan_build_args = []
+        self.use_clang_tidy = None
+        self.clang_tidy_args = []
 
         if platform.system() not in ('Darwin', 'FreeBSD', 'Linux'):
             self.lit_config.fatal("unrecognized system")
@@ -217,9 +303,20 @@
         conf = self.get_lit_conf(name)
         if conf is None:
             return None
-        if conf.lower() in ('1', 'true'):
+        if conf.lower() in ('1', 'true', 'on'):
             return True
-        if conf.lower() in ('', '0', 'false'):
+        if conf.lower() in ('', '0', 'false', 'off'):
+            return False
+        self.lit_config.fatal(
+            "parameter '{}' should be true or false".format(name))
+
+    def get_lit_switch(self, name):
+        s = self.get_lit_conf(name)
+        if s is None:
+            return False
+        elif s.lower() in ('', '1', 'true', 'on'):
+            return True
+        elif s.lower() in ('0', 'false', 'off'):
             return False
         self.lit_config.fatal(
             "parameter '{}' should be true or false".format(name))
@@ -229,22 +326,38 @@
         self.configure_triple()
         self.configure_src_root()
         self.configure_obj_root()
+        self.configure_test_root()
         self.configure_use_system_lib()
         self.configure_use_clang_verify()
-        self.configure_env()
         self.configure_std_flag()
         self.configure_compile_flags()
         self.configure_link_flags()
         self.configure_sanitizer()
+        self.configure_warnings()
+        self.configure_generate_coverage()
+        self.configure_scan_build()
+        self.configure_clang_tidy()
         self.configure_features()
+        self.lit_config.note('using compile_flags: %r' % self.compile_flags)
+        self.lit_config.note('using link_flags: %r' % self.link_flags)
+        self.lit_config.note('using available_features: %r' % self.config.available_features)
 
     def get_test_format(self):
         return LibcxxTestFormat(
             self.cxx,
-            self.use_clang_verify,
             cpp_flags=['-nostdinc++'] + self.compile_flags,
             ld_flags=['-nodefaultlibs'] + self.link_flags,
-            exec_env=self.env)
+            exec_env=self.env,
+            test_root=self.test_root,
+            use_verify_for_fail=self.use_clang_verify,
+            generate_coverage=self.generate_coverage,
+            coverage_flags=self.coverage_flags,
+            coverage_root=self.coverage_root,
+            use_scan_build=self.use_scan_build,
+            scan_build_output=self.scan_build_output,
+            scan_build_args=self.scan_build_args,
+            use_clang_tidy=self.use_clang_tidy,
+            clang_tidy_args=self.clang_tidy_args)
 
     def configure_cxx(self):
         # Gather various compiler parameters.
@@ -257,11 +370,10 @@
                                      self.config.environment['PATH'])
             if clangxx:
                 self.cxx = clangxx
-                self.lit_config.note(
-                    "inferred cxx_under_test as: %r" % self.cxx)
         if not self.cxx:
             self.lit_config.fatal('must specify user parameter cxx_under_test '
                                   '(e.g., --param=cxx_under_test=clang++)')
+        self.lit_config.note('using cxx_under_test as: %r' % self.cxx)
 
     def configure_src_root(self):
         self.src_root = self.get_lit_conf(
@@ -270,6 +382,9 @@
     def configure_obj_root(self):
         self.obj_root = self.get_lit_conf('libcxx_obj_root', self.src_root)
 
+    def configure_test_root(self):
+        self.test_root = str(os.path.realpath(os.path.join(self.src_root, 'test')))
+
     def configure_use_system_lib(self):
         # This test suite supports testing against either the system library or
         # the locally built one; the former mode is useful for testing ABI
@@ -279,17 +394,13 @@
         if self.use_system_lib is None:
             # Default to testing against the locally built libc++ library.
             self.use_system_lib = False
-            self.lit_config.note(
-                "inferred use_system_lib as: %r" % self.use_system_lib)
+        else:
+            self.lit_config.note('using use_system_lib as: %r' % self.use_system_lib)
 
     def configure_use_clang_verify(self):
         '''If set, run clang with -verify on failing tests.'''
-        self.use_clang_verify = self.get_lit_bool('use_clang_verify')
-        if self.use_clang_verify is None:
-            # TODO: Default this to True when using clang.
-            self.use_clang_verify = False
-            self.lit_config.note(
-                "inferred use_clang_verify as: %r" % self.use_clang_verify)
+        self.use_clang_verify = self.get_lit_switch('use_clang_verify')
+
 
     def configure_features(self):
         additional_features = self.get_lit_conf('additional_features')
@@ -359,54 +470,74 @@
             self.compile_flags += ['-D_LIBCPP_HAS_NO_MONOTONIC_CLOCK']
 
     def configure_compile_flags(self):
+        # Check if libcxx_headers is defined. If it is then use that as
+        # the location for the libcxx headers.
+        libcxx_headers = self.get_lit_conf('libcxx_headers',
+                                           self.src_root + '/include')
         # Configure extra compiler flags.
-        self.compile_flags += ['-I' + self.src_root + '/include',
+        self.compile_flags += ['-I' + libcxx_headers,
                                '-I' + self.src_root + '/test/support']
         if sys.platform.startswith('linux'):
             self.compile_flags += ['-D__STDC_FORMAT_MACROS',
                                    '-D__STDC_LIMIT_MACROS',
                                    '-D__STDC_CONSTANT_MACROS']
+        # Add extra compile flags as specified on the command line.
+        extra_flags = self.get_lit_conf('compile_flags')
+        if extra_flags:
+            self.compile_flags += shlex.split(extra_flags)
+
 
     def configure_link_flags(self):
-        # Configure library search paths
-        abi_library_path = self.get_lit_conf('abi_library_path', '')
-        self.link_flags += ['-L' + self.obj_root + '/lib']
-        if not self.use_system_lib:
-            self.link_flags += ['-Wl,-rpath', '-Wl,' + self.obj_root + '/lib']
+        # Configure libc++ library
+        libcxx_library = self.get_lit_conf('libcxx_library')
+        # Ignore and warn if use_system_lib is true and libcxx_library is specified.
+        if self.use_system_lib and libcxx_library:
+            self.lit_config.warning(
+                'Conflicting options detected: libcxx_library and use_system_lib')
+            libcxx_library = None
+        # Link to the specific libc++ library if specified. Otherwise link to -lc++
+        # and add the build directory as a search path if use_system_lib is False.
+        if libcxx_library:
+            self.link_flags += [libcxx_library, '-Wl,-rpath',
+                                '-Wl,' + os.path.dirname(libcxx_library)]
+        else:
+            self.link_flags += ['-lc++']
+            if not self.use_system_lib:
+                self.link_flags += ['-L' + self.obj_root + '/lib', '-Wl,-rpath',
+                                    '-Wl,' + self.obj_root + '/lib']
+
+        # Add a search path for the ABI library path if specified.
+        abi_library_path = self.get_lit_conf('abi_library_path')
         if abi_library_path:
             self.link_flags += ['-L' + abi_library_path,
                                 '-Wl,-rpath', '-Wl,' + abi_library_path]
-        # Configure libraries
-        self.link_flags += ['-lc++']
-        link_flags_str = self.get_lit_conf('link_flags')
-        if link_flags_str is None:
-            cxx_abi = self.get_lit_conf('cxx_abi', 'libcxxabi')
-            if cxx_abi == 'libstdc++':
-                self.link_flags += ['-lstdc++']
-            elif cxx_abi == 'libsupc++':
-                self.link_flags += ['-lsupc++']
-            elif cxx_abi == 'libcxxabi':
-                self.link_flags += ['-lc++abi']
-            elif cxx_abi == 'libcxxrt':
-                self.link_flags += ['-lcxxrt']
-            elif cxx_abi == 'none':
-                pass
-            else:
-                self.lit_config.fatal(
-                    'C++ ABI setting %s unsupported for tests' % cxx_abi)
-
-            if sys.platform == 'darwin':
-                self.link_flags += ['-lSystem']
-            elif sys.platform.startswith('linux'):
-                self.link_flags += ['-lgcc_eh', '-lc', '-lm', '-lpthread',
-                                    '-lrt', '-lgcc_s']
-            elif sys.platform.startswith('freebsd'):
-                self.link_flags += ['-lc', '-lm', '-pthread', '-lgcc_s']
-            else:
-                self.lit_config.fatal("unrecognized system: %r" % sys.platform)
 
-            self.lit_config.note(
-                "inferred link_flags as: %r" % self.link_flags)
+        cxx_abi = self.get_lit_conf('cxx_abi', 'libcxxabi')
+        if cxx_abi == 'libstdc++':
+            self.link_flags += ['-lstdc++']
+        elif cxx_abi == 'libsupc++':
+            self.link_flags += ['-lsupc++']
+        elif cxx_abi == 'libcxxabi':
+            self.link_flags += ['-lc++abi']
+        elif cxx_abi == 'libcxxrt':
+            self.link_flags += ['-lcxxrt']
+        elif cxx_abi == 'none':
+            pass
+        else:
+            self.lit_config.fatal(
+                'C++ ABI setting %s unsupported for tests' % cxx_abi)
+
+        if sys.platform == 'darwin':
+            self.link_flags += ['-lSystem']
+        elif sys.platform.startswith('linux'):
+            self.link_flags += ['-lgcc_eh', '-lc', '-lm', '-lpthread',
+                                '-lrt', '-lgcc_s']
+        elif sys.platform.startswith('freebsd'):
+            self.link_flags += ['-lc', '-lm', '-pthread', '-lgcc_s']
+        else:
+            self.lit_config.fatal("unrecognized system: %r" % sys.platform)
+
+        link_flags_str = self.get_lit_conf('link_flags')
         if link_flags_str:
             self.link_flags += shlex.split(link_flags_str)
 
@@ -423,8 +554,8 @@
         self.config.available_features.add(std)
 
     def configure_sanitizer(self):
-        san = self.get_lit_conf('llvm_use_sanitizer', '').strip()
-        if san:
+        san = self.get_lit_conf('use_sanitizer').strip()
+        if san and san != 'None':
             self.compile_flags += ['-fno-omit-frame-pointer']
             if sys.platform.startswith('linux'):
                 self.link_flags += ['-ldl']
@@ -438,12 +569,67 @@
                 self.config.available_features.add('msan')
             elif san == 'Undefined':
                 self.compile_flags += ['-fsanitize=undefined',
-                                       '-fno-sanitize=vptr,function',
-                                       '-fno-sanitize-recover']
+                              '-fno-sanitize=vptr,function',
+                              '-fno-sanitize-recover']
                 self.config.available_features.add('ubsan')
             else:
                 self.lit_config.fatal('unsupported value for '
-                                      'libcxx_use_san: {0}'.format(san))
+                                      'use_sanitizer: {0}'.format(san))
+
+    def configure_warnings(self):
+        enable_warnings = self.get_lit_bool('enable_warnings')
+        if enable_warnings:
+            self.lit_config.note('Enabling warnings')
+            self.compile_flags += ['-Wall', '-Wextra', '-pedantic',
+                                   '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER']
+
+    def configure_generate_coverage(self):
+        self.generate_coverage = self.get_lit_bool('generate_coverage')
+        if self.generate_coverage:
+            self.coverage_flags = ['-g', '-O0', '--coverage', '-fprofile-arcs', '-ftest-coverage']
+            self.coverage_root = self.get_lit_conf('coverage_root', None)
+            if not self.coverage_root:
+                self.lit_config.fatal("'%s' is not a valid value for coverage_root" % self.coverage_root)
+            self.lit_config.note('outputing code coverage to: %s' % self.coverage_root)
+
+    def configure_scan_build(self):
+        self.use_scan_build = self.get_lit_conf('use_scan_build')
+        if self.use_scan_build is None:
+            return
+        if self.use_scan_build == '':
+            self.use_scan_build = 'scan-build'
+        self.lit_config.note(
+            'Using scan-build: %s' % self.use_scan_build)
+        output = self.get_lit_conf('scan_build_output')
+        if output is None:
+            output = tempfile.mkdtemp(suffix='', prefix='libcxx-scan-build-')
+        self.lit_config.note('Writing scan-build output to: %s' % output)
+        self.scan_build_output = output
+        args = self.get_lit_conf('scan_build_args')
+        if args:
+            args = shlex.split(args)
+        else:
+            args = ['-analyze-headers']
+        self.lit_config.note('Using scan-build args: %r' % args)
+        self.scan_build_args = args
+
+
+    def configure_clang_tidy(self):
+        self.use_clang_tidy = self.get_lit_conf('use_clang_tidy')
+        if self.use_clang_tidy is None:
+            return
+        if self.use_clang_tidy == '':
+            self.use_clang_tidy = 'clang-tidy'
+        self.lit_config.note(
+            'Using clang-tidy: %s' % self.use_clang_tidy)
+        args = self.get_lit_conf('clang_tidy_args')
+        if args is not None:
+            self.clang_tidy_args = shlex.split(args)
+        else:
+            self.clang_tidy_args = ["-checks=-*,llvm*,clang-analyzer*,-clang-analyzer-alpha*",
+                                    "-header-filter='.*'"]
+        self.lit_config.note('Using clang-tidy args: %r' % self.clang_tidy_args)
+
 
     def configure_triple(self):
         # Get or infer the target triple.
@@ -452,7 +638,7 @@
         # under test.
         if not self.config.target_triple:
             target_triple = lit.util.capture(
-                [self.cxx, '-dumpmachine']).strip()
+                 [self.cxx, '-dumpmachine']).strip()
             # Drop sub-major version components from the triple, because the
             # current XFAIL handling expects exact matches for feature checks.
             # Example: x86_64-apple-darwin14.0.0 -> x86_64-apple-darwin14
@@ -467,15 +653,8 @@
                target_triple.endswith('suse-linux'):
                 target_triple += '-gnu'
             self.config.target_triple = target_triple
-            self.lit_config.note(
-                "inferred target_triple as: %r" % self.config.target_triple)
-
-    def configure_env(self):
-        # Configure extra linker parameters.
-        if sys.platform == 'darwin':
-            if not self.use_system_lib:
-                self.env['DYLD_LIBRARY_PATH'] = os.path.join(self.obj_root,
-                                                             'lib')
+        self.lit_config.note(
+                "using target_triple: %r" % self.config.target_triple)
 
 
 # name: The name of this test suite.
Index: test/lit.site.cfg.in
===================================================================
--- test/lit.site.cfg.in
+++ test/lit.site.cfg.in
@@ -6,8 +6,10 @@
 config.python_executable     = "@PYTHON_EXECUTABLE@"
 config.enable_shared         = @LIBCXX_ENABLE_SHARED@
 config.cxx_abi               = "@LIBCXX_CXX_ABI_LIBNAME@"
-config.llvm_use_sanitizer    = "@LLVM_USE_SANITIZER@"
 config.abi_library_path      = "@LIBCXX_CXX_ABI_LIBRARY_PATH@"
+config.use_sanitizer         = "@LLVM_USE_SANITIZER@"
+config.generate_coverage     = "@LIBCXX_GENERATE_COVERAGE@"
+config.coverage_root         = "@LIBCXX_COVERAGE_DIR@"
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@LIBCXX_SOURCE_DIR@/test/lit.cfg")
Index: www/index.html
===================================================================
--- www/index.html
+++ www/index.html
@@ -473,6 +473,7 @@
 <li><a href="type_traits_design.html"><tt>&lt;type_traits&gt;</tt></a></li>
 <li><a href="http://cplusplusmusings.wordpress.com/2012/07/05/clang-and-standard-libraries-on-mac-os-x/">Excellent notes by Marshall Clow</a></li>
 <li><a href="debug_mode.html">Status of debug mode</a></li>
+<li><a href="lit_usage.html">Using LIT on the command line</a></li>
 </ul>
 
 </div>
Index: www/lit_usage.html
===================================================================
--- /dev/null
+++ www/lit_usage.html
@@ -0,0 +1,227 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+          "http://www.w3.org/TR/html4/strict.dtd">
+<!-- Material used from: HTML 4.01 specs: http://www.w3.org/TR/html401/ -->
+<html>
+<head>
+  <META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
+  <title>Testing libc++ using LIT</title>
+  <link type="text/css" rel="stylesheet" href="menu.css">
+  <link type="text/css" rel="stylesheet" href="content.css">
+  <style>
+    .lit-option {
+      padding-top: 0.5em;
+      margin-bottom: 0.0em;
+      font-size: medium;
+      color:#2d58b7
+    }
+    .lit-option-desc {
+      display: block;
+      margin-top: 0em;
+      margin-bottom: 0em;
+      margin-left: 20px;
+      margin-right: 20px;
+    }
+  </style>
+</head>
+
+<body>
+<div id="menu">
+  <div>
+    <a href="http://llvm.org/">LLVM Home</a>
+  </div>
+
+  <div class="submenu">
+    <label>libc++ Info</label>
+    <a href="/index.html">About</a>
+  </div>
+
+  <div class="submenu">
+    <label>Quick Links</label>
+    <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev</a>
+    <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits</a>
+    <a href="http://llvm.org/bugs/">Bug Reports</a>
+    <a href="http://llvm.org/svn/llvm-project/libcxx/trunk/">Browse SVN</a>
+    <a href="http://llvm.org/viewvc/llvm-project/libcxx/trunk/">Browse ViewVC</a>
+  </div>
+</div>
+
+<div id="content">
+<!--*********************************************************************-->
+                     <h1>Testing libc++ using LIT</h1>
+<!--*********************************************************************-->
+<p>
+libc++ uses LIT to configure and run it's tests. The primary way to run the
+libc++ tests is by using <code>make check-libcxx</code>. However since libc++
+can be used in any number of possible configurations it is important to
+customize the way LIT builds and runs the tests. This guide provides
+information on how to use LIT directly to test libc++.
+</p>
+<p>
+Documentation for LIT can be found
+<a href='http://llvm.org/docs/CommandGuide/lit.html'>here</a>.
+</p>
+
+<!--*********************************************************************-->
+                        <h2>Getting Started</h2>
+<!--*********************************************************************-->
+<p>
+After building libc++ use the following commands before you start using LIT to
+test.
+</p>
+<ul>
+  <li><code>alias lit='python path/to/llvm/utils/lit/lit.py'</code></li>
+  <li><code>ln -s path/to/libcxx-build/test/lit.site.cfg path/to/libcxx/test/lit.site.cfg</code></li>
+</ul>
+<p>
+You can now run the libc++ tests by running:
+</p>
+<ul>
+  <li><code>cd path/to/libcxx</code></li>
+  <li><code>lit -sv ./test</code></li>
+</ul>
+<p>
+To only run a subsection of the tests use:
+<ul>
+  <li><code>lit -sv test/numerics # Run only the numeric tests</code></li>
+</ul>
+
+<!--*********************************************************************-->
+                     <h2>Customization Options</h2>
+<!--*********************************************************************-->
+<p>
+libc++'s testsuite provides multiple options to configure the way the tests
+are build and run. To use these options you pass them on the LIT command line
+as <code>--param NAME</code> or <code>--param NAME=VALUE</code>. Some options
+have default values specified during CMake's configuration. Passing the option
+on the command line will override the default.
+</p>
+
+<p>
+<h3 class="lit-option">libcxx_headers=&lt;path/to/headers&gt;</h3>
+<blockquote class="lit-option-desc">
+Specify the libc++ headers that are tested. By default the headers in the source
+tree are used.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">libcxx_library=&lt;path/to/libc++.so&gt;</h3>
+<blockquote class="lit-option-desc">
+Specify the libc++ library that is tested. By default the library in the build
+directory is used. This option has no effect if <code>use_system_lib</code> is provided.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">use_system_lib=&lt;bool&gt;</h3>
+<blockquote class="lit-option-desc">
+<b>Default: </b><code>False</code></br>
+Enable or disable testing against the installed version of libc++ library.
+Note: This does not use the installed headers.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">compile_flags="&lt;list-of-args&gt;"</h3>
+<blockquote class="lit-option-desc">
+Specify an additional list of compile flags to use.
+Note: This options should not be used to change the standard version used.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">link_flags="&lt;list-of-args&gt;"</h3>
+<blockquote class="lit-option-desc">
+Specify an additional list of linker flags to use.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">std=&lt;standard version&gt;</h3>
+<blockquote class="lit-option-desc">
+<b>Values: </b><code>c++98, c++03, c++11, c++1z, c++14</code></br>
+Change the standard version used when building the tests.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">use_sanitizer=&lt;sanitizer name&gt;</h3>
+<blockquote class="lit-option-desc">
+<b>Values: </b><code>Memory, MemoryWithOrigins, Address, Undefined, None</code></br>
+Run the tests using the given sanitizer. If <code>LLVM_USE_SANITIZER</code>
+was given when building libc++ then that sanitizer will be used by default.
+If <code>None</code> is given then no sanitizer will be used.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">enable_warnings[=&lt;bool&gt;]</h3>
+<blockquote class="lit-option-desc">
+<b>Default: </b><code>False</code><br>
+Enable <code>-Wall -Wextra -pedantic</code> as well as disabling
+the system header pragmas.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">use_clang_verify[=&lt;bool&gt;]</h3>
+<blockquote class="lit-option-desc">
+<b>Default: </b><code>False</code><br>
+Enable the use of clang verif on tests that expect a compilation error.
+This verifies that the test fails to compile for the right reason.
+</blockquote>
+</p>
+
+<h2>Scan Build Options</h2>
+
+<p>
+<h3 class="lit-option">use_scan_build[=&lt;path/to/scan-build&gt;]</h3>
+<blockquote class="lit-option-desc">
+When specified the tests are compiled through scan-build. The optional value is
+used to specify the scan-build executable to use. If scan-build finds a defect
+the test will fail.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">scan_build_output=&lt;path/to/scan-build/output&gt;</h3>
+<blockquote class="lit-option-desc">
+Specify a folder in which to store the scan-build output. If scan-build is
+used without this option a temporary directory is created and reported at the
+start of the LIT run.
+</blockquote>
+</p>
+
+<p>
+<h3 class="lit-option">scan_build_args="&lt;list-of-args&gt;"</h3>
+<blockquote class="lit-option-desc">
+<b>Default: </b><code>-analyze-headers</code><br>
+Specify a list of args to be passed to <code>scan-build</code>.
+</blockquote>
+</p>
+
+<h2>Clang Tidy Options</h2>
+
+<p>
+<h3 class="lit-option">use_clang_tidy[=&lt;path/to/clang-tidy&gt;</h3>
+<blockquote class="lit-option_desc">
+When specified the tests are run through clang-tidy as an extra step. The test
+will fail if clang-tidy produces any output. The option value is used to specify
+the clang-tidy executable to use.
+</blockquote>
+</p>
+
+
+<p>
+<h3 class="lit-option">clang_tidy_args="&lt;list-of-args&gt;"</h3>
+<blockquote class="lit-option_desc">
+<b>Default: </b><code>-checks=-*,llvm*,clang-analyzer*,-clang-analyzer-alpha*
+                      -header-filter='.*'</code><br>
+Specify a list of args to be passed to <code>clang-tidy</code>.
+</blockquote>
+</p>
+
+
+</div>
+</body>
+</html>